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From: Peter Todd <pete@petertodd.org>
To: Andrew Poelstra <apoelstra@wpsoftware.net>,
	Bitcoin Protocol Discussion
	<bitcoin-dev@lists.linuxfoundation.org>
Subject: Re: [bitcoin-dev] Compressed Bitcoin Transactions
Date: Tue, 5 Sep 2023 18:00:33 +0000	[thread overview]
Message-ID: <ZPdswQ7uAJr35YbC@petertodd.org> (raw)
In-Reply-To: <ZPHtgiJQ4Yqrr941@camus>

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On Fri, Sep 01, 2023 at 01:56:18PM +0000, Andrew Poelstra via bitcoin-dev wrote:
> We can swag what the space savings would be: there are 122MM utxos right
> now, which is a bit under 2^27. So assuming a uniform distribution of
> prefixes we'd need to specify 28 bits to identify a UTXO. To contrast,
> to identify a blockheight we need 20 bits and then maybe 12 more bits to
> specify a TXO within a block. Plus whatever varint overhead we have.
> (I've been working on this project but busy with family stuff and don't
> remember exactly where we landed on the varints for this. I think we
> agreed that there was room for improvement but didn't want to hold up
> posting the rest of the concept because of it.)

Since most transactions spend txouts that are similar in height to each other,
you could save further bits by specifying a reference height and then encoding
the exact txout with a delta.

If you're sending multiple txins or multiple transactions in a single packet,
you could achieve this by starting the packet with the reference block height.

If your application tends to send just a single transaction, you could use a
reference height that is a function of the current time. Since sender and
receiver might not agree on the exact time, you could try slightly difference
reference heights via bruteforcing until the transaction signatures validate.

-- 
https://petertodd.org 'peter'[:-1]@petertodd.org

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  parent reply	other threads:[~2023-09-05 18:00 UTC|newest]

Thread overview: 16+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2023-08-31 21:30 [bitcoin-dev] Compressed Bitcoin Transactions Tom Briar
2023-09-01  0:49 ` Andrew Poelstra
2023-09-01 10:24 ` Fabian
2023-09-01 10:43   ` Fabian
2023-09-01 13:56   ` Andrew Poelstra
2023-09-01 14:12     ` Tom Briar
2023-09-05 18:00     ` Peter Todd [this message]
2023-09-05 18:30       ` Tom Briar
2024-01-05 15:06         ` Tom Briar
2024-01-05 15:19           ` Andrew Poelstra
2024-01-09 15:31             ` Tom Briar
2024-01-16 17:08               ` Tom Briar
2024-01-18  9:24                 ` Jonas Schnelli
2024-01-19 21:09                   ` Tom Briar
2023-09-01 16:56 ` Jonas Schnelli
2023-09-01 17:05   ` Tom Briar

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